The US administration stepped up economic pressure on Mahmoud Ahmadinejad's eccentric government less than two weeks ago.

A Yahoo! spokeswoman told The Reg: "Yahoo! continually reviews its business operations to ensure compliance with these restrictions. Consistent with this policy, we cannot accept registrations from countries subject to these restrictions.

So essentially, you can't choose Iran as a country option because we are restricted from conducting business there – all US companies must comply with this policy." She was unable to tell us exactly when Yahoo! applied the rules.

Microsoft said it was unable to comment on the issue.

Google insists the sanctions do not preclude it from including Iran in its Gmail country list. A statement from the firm said: "Google is committed to full compliance with US export controls and sanctions programs and is confident in our compliance with those controls and programs."

A representative of the Iranian embassy in London was unable to provide an immediate response.

On 30 October, the Tehran correspondent of Netherlands newspaper NRC Handelsbladreported (in Dutch) that his paid Skype account had been cancelled. An email from the VoIP outfit said its financial services provider had been forced to stop taking payments from Iran.

That's perhaps more easily understandable than a blockade on free email. Whether Yahoo! and Microsoft's apparent action is the result of an over-zealous compliance lawyer or not, the effect on US interests of denying ordinary Iranians access to free international communications is questionable at best.

Of course, the Iranian government itself heavily restricts what its citizens can access online. The OpenNet Initiative, a collaboration of Harvard, Toronto, Oxford, and Cambridge universities, describes it as having installed "one of the most extensive technical filtering systems in the world". ®

Update

Yahoo! got back to us with details of when the change was made:

"In June of this year, Yahoo! updated this [user information gathering] process to capture more relevant information about new users in order to provide more personalized services for users and more targeted advertising for its customers. The user information requested includes country of residence. Because the United States restricts U.S. businesses from conducting business in certain countries, Yahoo! also ensured that these countries do not appear in the drop down menu."